1. Technical Field
This invention relates generally to the field of semiconductors and, more particularly, to approaches for incorporating niobium carbide (NbC) as a multi-function layer (e.g., a work function and a gate metal layer) into gate stacks that are used for field effect transistors (FET) in semiconductor devices.
2. Related Art
In the semiconductor industry, transistors such as field effect transistors (FETs) are commonly utilized as integral parts of the devices. A FET may have both n-FET and p-FET components on which a set of gate stacks may be formed. In a typical assembly, these gate stacks may include various combinations of layers such as a high-k layer, work function (WF) layers such as titanium nitride (TiN) on p-FET and tantalum carbide (TaC) on n-FET, a gate metal such as tungsten (W) or aluminum (Al) and a capping layer. Moreover, different work function metals are typically required for n-FET versus p-FET gate stacks. Because the gate stacks may include different layers and/or compounds, various processing steps are generally required to form such devices. Such steps may include depositing layers, etching layers, forming recesses in layers to increase the volume to be filled by the gate metal, polishing layers, etc.
Challenges may exist, however, in that such integration schemes are often complicated and error prone. For example, it is difficult to recess a gate stack in which multiple layers need to be etched simultaneously. For example, a p-FET and/or n-FET gate stack will often require three or more layers to be etched simultaneously. When the recessing process is done unevenly, device errors may occur. As such, a need exists for a more simplified and reliable integration scheme.